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\"     @(#)getgrent.3   8.2 (Berkeley) 4/19/94
\"
Dd February 7, 2018
Dt GETGRENT 3
Os
Sh NAME
Nm getgrent ,
Nm getgrent_r ,
Nm getgrgid ,
Nm getgrgid_r ,
Nm getgrnam ,
Nm getgrnam_r ,
Nm setgroupent ,
\" .Nm setgrfile ,
Nm setgrent ,
Nm endgrent
Nd group database operations
Sh LIBRARY
Lb libc
Sh SYNOPSIS
In grp.h
Ft struct group *
Fn getgrent void
Ft int
Fo getgrent_r
Fa "struct group *grp"
Fa "char *buffer"
Fa "size_t buflen"
Fa "struct group **result"
Fc
Ft struct group *
Fn getgrgid "gid_t gid"
Ft int
Fo getgrgid_r
Fa "gid_t gid"
Fa "struct group *grp"
Fa "char *buffer"
Fa "size_t buflen"
Fa "struct group **result"
Fc
Ft struct group *
Fn getgrnam "const char *name"
Ft int
Fo getgrnam_r
Fa "const char *name"
Fa "struct group *grp"
Fa "char *buffer"
Fa "size_t buflen"
Fa "struct group **result"
Fc
Ft int
Fn setgroupent "int stayopen"
\" .Ft void
\" .Fn setgrfile "const char *name"
Ft void
Fn setgrent void
Ft void
Fn endgrent void
Sh DESCRIPTION
These functions operate on the group database which is described in
Xr group 5 .
Each line of the database is defined by the structure
Ar group
found in the include
file
In grp.h :
Bd -literal -offset indent
struct group {
       char    *gr_name;       /* group name */
       char    *gr_passwd;     /* group password */
       gid_t   gr_gid;         /* group id */
       char    **gr_mem;       /* group members */
};
Ed
Pp
The functions
Fn getgrnam
and
Fn getgrgid
search the group database for the given group name pointed to by
Ar name
or the group id pointed to by
Ar gid ,
respectively, returning the first one encountered.
Identical group names or group ids may result in undefined behavior.
Pp
The
Fn getgrent
function sequentially reads the group database and is intended for programs
that wish to step through the complete list of groups.
Pp
All three functions will open the group file for reading, if necessary.
Pp
The functions
Fn getgrnam_r ,
Fn getgrgid_r ,
and
Fn getgrent_r
act like their non re-entrant counterparts
respectively, updating the contents of
Ar grp
and storing a pointer to that in
Ar result ,
and returning
Dv 0 .
Storage used by
Ar grp
is allocated from
Ar buffer ,
which is
Ar buflen
bytes in size.
If the requested entry cannot be found,
Ar result
will point to
Dv NULL
and
Dv 0
will be returned.
If an error occurs,
a non-zero error number will be returned and
Ar result
will point to
Dv NULL .
Calling
Fn getgrent_r
from multiple threads will result in each thread reading a disjoint portion
of the group database.
Pp
The
Fn setgroupent
function opens the file, or rewinds it if it is already open.
If
Fa stayopen
is non-zero, file descriptors are left open, significantly speeding
functions subsequent calls.
This functionality is unnecessary for
Fn getgrent
as it doesn't close its file descriptors by default.
It should also be noted that it is dangerous for long-running
programs to use this functionality as the group file may be updated.
Pp
The
Fn setgrent
function is equivalent to
Fn setgroupent
with an argument of zero.
Pp
The
Fn endgrent
function closes any open files.
Sh RETURN VALUES
The functions
Fn getgrgid ,
Fn getgrnam ,
and
Fn getgrent
return a valid pointer to a group structure on success
and a
Dv NULL
pointer if the entry was not found or an error occurred.
If an error occurred, the global variable
Dv errno
is set to indicate the nature of the failure.
Pp
The functions
Fn getgrgid_r ,
Fn getgrnam_r ,
and
Fn getgrent_r
return
Dv 0
on success or entry not found, and non-zero on failure, setting the global
variable
Dv errno
to indicate the nature of the failure.
Pp
The
Fn setgroupent
function returns the value 1 if successful, otherwise the value
0 is returned, setting the global variable
Dv errno
to indicate the nature of the failure.
Pp
The
Fn endgrent
and
Fn setgrent
functions have no return value.
Sh FILES
Bl -tag -width /etc/group -compact
It Pa /etc/group
group database file
El
Sh COMPATIBILITY
The historic function
Fn setgrfile ,
which allowed the specification of alternative group databases, has
been deprecated and is no longer available.
Sh ERRORS
The following error codes may be set in
Va errno
for
Nm getgrent ,
Nm getgrent_r ,
Nm getgrnam ,
Nm getgrnam_r ,
Nm getgrgid ,
Nm getgrgid_r ,
and
Nm setgroupent :
Bl -tag -width Er
It Bq Er EINTR
A signal was caught during the database search.
It Bq Er EIO
An I/O error has occurred.
It Bq Er EMFILE
The limit on open files for this process has been reached.
It Bq Er ENFILE
The system limit on open files has been reached.
El
Pp
The following error code may be set in
Va errno
for
Nm getgrent_r ,
Nm getgrnam_r ,
and
Nm getgrgid_r :
Bl -tag -width Er
It Bq Er ERANGE
The resulting
Ft struct group
does not fit in the space defined by
Dv buffer
and
Dv buflen
El
Pp
Other
Dv errno
values may be set depending on the specific database backends.
Sh SEE ALSO
Xr getpwent 3 ,
Xr group 5 ,
Xr nsswitch.conf 5
Sh STANDARDS
The
Fn getgrgid
and
Fn getgrnam
functions conform to
St -p1003.1-90 .
The
Fn getgrgid_r
and
Fn getgrnam_r
functions conform to
St -p1003.1c-95 .
The
Fn endgrent ,
Fn getgrent ,
and
Fn setgrent
functions conform to
St -xpg4.2
and
St -p1003.1-2004
(XSI extension).
Sh HISTORY
The functions
Fn endgrent ,
Fn getgrent ,
Fn getgrgid ,
Fn getgrnam ,
and
Fn setgrent
appeared in
At v7 .
The functions
Fn setgrfile
and
Fn setgroupent
appeared in
Bx 4.3 Reno .
The functions
Fn getgrgid_r
and
Fn getgrnam_r
appeared in
Nx 3.0 .
Sh BUGS
The functions
Fn getgrent ,
Fn getgrgid ,
Fn getgrnam ,
Fn setgroupent
and
Fn setgrent
leave their results in an internal static object and return
a pointer to that object.
Subsequent calls to the same function will modify the same object.
Pp
The functions
Fn getgrent ,
Fn endgrent ,
Fn setgroupent ,
and
Fn setgrent
are fairly useless in a networked environment and should be
avoided, if possible.
Fn getgrent
makes no attempt to suppress duplicate information if multiple
sources are specified in
Xr nsswitch.conf 5

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